Systems and methods for improving connections to an information handling system

ABSTRACT

System and methods for improving connections to an information handling system are disclosed. An enhanced serial attached small computer system interface for an information handling system includes a receptacle which is connectable to an information handling system and a connector which is connectable to the receptacle. The connector comprises a first set of signal pins positioned on a first planar surface of the connector and a second set of signal pins positioned on a second planar surface of the connector. The second planar surface is not co-planar with the first planar surface. The connector further includes a third set of signal pins positioned on a third planar surface of the connector and the third planar surface is not co-planar with the first planar surface and the second planar surface.

TECHNICAL FIELD

The present disclosure relates generally to information handling systemsand, more particularly, to system and methods for improving connectionsto an information handling system.

BACKGROUND

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to these users is an information handling system.An information handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may vary with respect to the type of informationhandled; the methods for handling the information; the methods forprocessing, storing or communicating the information; the amount ofinformation processed, stored, or communicated; and the speed andefficiency with which the information is processed, stored, orcommunicated. The variations in information handling systems allow forinformation handling systems to be general or configured for a specificuser or specific use such as financial transaction processing, airlinereservations, enterprise data storage, or global communications. Inaddition, information handling systems may include or comprise a varietyof hardware and software components that may be configured to process,store, and communicate information and may include one or more computersystems, data storage systems, and networking systems.

Flash memory is a non-volatile data storage device that can beelectronically erased and reprogrammed. The performance of aninformation handling system, such as a server, may be improved by usingflash memory which provides bulk storage and/or high speed caching. AFlash Solid-State Drive (“SSD”) is a type of flash memory that usessolid-state memory to store persistent data. An SSD emulates a hard diskdrive interface and may replace it in many applications.

Small Computer System Interface (“SCSI”) is a set of standards forphysically connecting and transferring data between information handlingsystems and peripheral devices such as data storage devices. SerialAttached SCSI (“SAS”) is an evolution of the traditional SCSI into apoint-to-point serial peripheral interface in which controllers arelinked directly to disk drives. SAS provides an improvement over thetraditional SCSI because it enables multiple devices of different sizesand types to be connected simultaneously with thinner and longer cables.In addition, SAS drives can be hot-plugged. Specifically, SAS drives maybe connected to or removed from an information handling system while theinformation handling system is running and the operating system of theinformation handling system can recognize that change.

Advanced Technology Attachment (“ATA”) is another disk driveimplementation for an information handling system that integrates thecontroller on the disk drive itself. Serial ATA (“SATA”) is an evolutionof the traditional ATA and is a serial link, typically consisting of asingle cable with a minimum of four wires. The SATA creates apoint-to-point connection between devices. The thin SATA cablesfacilitate more efficient air flow inside a form factor and also allowfor smaller chassis designs. The term “form factor” refers to thephysical shape and size of a device and may be used to describe the sizeof a circuit board.

Typically, the capabilities of SAS and SATA Flash SSDs may be limited bythe interface. Specifically, the single or dual SATA or SAS lanes to theend data storage device may adversely impact system operations bycausing latency and limiting throughput. Similarly, Flash Solid StateCards or Peripheral Component Interconnect Express (“PCIe”) Flash cardsare limited by the confines of its form factor which supports hot plugbut not in a manner acceptable to system users.

Hot plug in a data center environment is preferably achieved throughfront or back loading modules. The current high performance storage formfactor is the 2.5 inch hard disk drive. It is desirable to put PCIe SSDsin this form factor for system design and customer usage. However, froma system design perspective, co-locating two different connectors ischallenging due to the need for front to back airflow in data centerhardware. Specifically, two physical connectors, one for SAS devices andone for PCIe devices, block any opportunity for cooling vent holes inthe storage device backplanes.

SUMMARY

The present disclosure relates generally to information handling systemsand, more particularly, to system and methods for improving connectionsto an information handling system.

In one exemplary embodiment, the present invention is directed to anenhanced serial attached small computer system interface for aninformation handling system comprising: a receptacle; wherein thereceptacle is connectable to an information handling system; and aconnector; wherein the connector is connectable to the receptacle; andwherein the connector comprises: a first set of signal pins positionedon a first planar surface of the connector; a second set of signal pinspositioned on a second planar surface of the connector; wherein thesecond planar surface is not co-planar with the first planar surface;and a third set of signal pins positioned on a third planar surface ofthe connector; wherein the third planar surface is not co-planar withthe first planar surface and the second planar surface.

In another exemplary embodiment, the present invention is directed to amethod of selectively transferring data over a PCIe path or a SAS pathcomprising: connecting an enhanced connector with a first set ofconnection lanes and a second set of connection lanes to one or morecontrollers; wherein the controller controls the connection lanes;wherein the first set of connection lanes are operable as a PCIe signalpath; wherein the second set of connection lanes are operable as a SASsignal path; connecting the first set of connection lanes to a PCIe datastorage device; and connecting the second set of connection lanes to aSAS data storage device.

In another exemplary embodiment, the present invention is directed to amethod of selectively transferring data over a PCIe path or a SAS pathcomprising: connecting an enhanced connector with a first set ofconnection lanes and a second set of connection lanes connected to oneor more controllers; wherein the one or more controllers control theconnection lanes; wherein the first set of connection lanes are operableas a PCIe signal path; wherein the second set of connection lanes areoptionally operable as a SAS signal path or a PCIe signal path;connecting the first set of connection lanes to a PCIe data storagedevice; and connecting the second set of connection lanes to a datastorage device selected from the group consisting of a SAS data storagedevice and a PCIe data storage device.

Thus, the present disclosure provides apparatuses and methods forimproving connections to an information handling system. Other technicaladvantages will be apparent to those of ordinary skill in the art inview of the specification, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 is a block diagram showing an information handling system inaccordance with certain embodiments of the present disclosure;

FIG. 2 is a perspective view of a SAS drive plug connector (“SASConnector”) in accordance with the prior art.

FIG. 3 is a side view of a receptacle of the SAS Connector of FIG. 2.

FIG. 4 is a chart of the pin count for a SAS connector in accordancewith the prior art.

FIG. 5 is a perspective view of a SAS drive plug connector (“SASConnector”) in accordance with an embodiment of the present invention.

FIG. 6 is a side view of a receptacle of the SAS Connector of FIG. 5.

FIG. 7 is a chart of the pin count for a SAS connector in accordancewith the present invention.

FIG. 8 depicts the operation of a SAS drive plug connector in accordancewith one exemplary embodiment of the present invention.

FIG. 9 depicts the operation of a SAS drive plug connector in accordancewith another exemplary embodiment of the present invention.

While embodiments of this disclosure have been depicted and describedand are defined by reference to example embodiments of the disclosure,such references do not imply a limitation on the disclosure, and no suchlimitation is to be inferred. The subject matter disclosed is capable ofconsiderable modification, alteration, and equivalents in form andfunction, as will occur to those skilled in the pertinent art and havingthe benefit of this disclosure. The depicted and described embodimentsof this disclosure are examples only, and not exhaustive of the scope ofthe disclosure.

DETAILED DESCRIPTION

For purposes of this disclosure, an information handling system mayinclude any instrumentality or aggregate of instrumentalities operableto compute, classify, process, transmit, receive, retrieve, originate,switch, store, display, manifest, detect, record, reproduce, handle, orutilize any form of information, intelligence, or data for business,scientific, control, or other purposes. For example, an informationhandling system may be a personal computer, a network storage device, orany other suitable device and may vary in size, shape, performance,functionality, and price. The information handling system may includerandom access memory (RAM), one or more processing resources such as acentral processing unit (CPU) or hardware or software control logic,ROM, and/or other types of nonvolatile memory. Additional components ofthe information handling system may include one or more disk drives, oneor more network ports for communication with external devices as well asvarious input and output (I/O) devices, such as a keyboard, a mouse, anda video display. The information handling system may also include one ormore buses operable to transmit communications between the varioushardware components.

Illustrative embodiments of the present invention are described indetail below. In the interest of clarity, not all features of an actualimplementation are described in this specification. It will of course beappreciated that in the development of any such actual embodiment,numerous implementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthe present disclosure.

FIG. 1 illustrates a block diagram of an example information handlingsystem 100, in accordance with certain embodiments of the presentdisclosure. In certain embodiments, information handling system 100 maybe a personal computer (e.g., a desktop computer, workstation orportable computer), storage enclosure or server. As depicted in FIG. 1,information handling system 100 may include a processor 105, a systemmemory 110 communicatively coupled to processor 105, an I/O hub 115communicatively coupled to processor 105, storage 120 communicativelycoupled to I/O hub 115, nonvolatile memory 125 communicatively coupledto I/O hub 115, and firmware 130 communicatively coupled to I/O hub 115.

Processor 105 may include any system, device, or apparatus configured tointerpret and/or execute program instructions and/or process data, andmay include, without limitation a microprocessor, microcontroller,digital signal processor (DSP), application specific integrated circuit(ASIC), or any other digital or analog circuitry configured to interpretand/or execute program instructions and/or process data. In someembodiments, processor 105 may interpret and/or execute programinstructions and/or process data stored in system memory 110, storagemedia 120 and/or another component of information handling system 100.Processor 105 may be coupled to other components (not shown) withoptional interfaces (I/Fs) via a PCIe interface, for example.

System memory 110 may be communicatively coupled to processor 105, forexample, via a DDRn (a version of a double-date-rate type) interface.System memory 110 may include any system, device, or apparatusconfigured to retain program instructions and/or data for a period oftime (e.g., computer-readable media). System memory 110 may includerandom access memory (RAM), electrically erasable programmable read-onlymemory (EEPROM), a PCMCIA card, flash memory, magnetic storage,opto-magnetic storage, or any suitable selection and/or array ofvolatile memory. Note that apparatuses and methods described may applyto the volatile portions of system memory 110.

Processor 105 may be coupled to an I/O hub 115 via a host link, forexample. I/O hub 115 may be communicatively coupled to storage 120 via,for example, a SCSI, Internet SCSI (iSCSI), SAS or any other transportthat operates with the SCSI protocol, ATA, SATA, advanced technologyattachment packet interface (ATAPI), serial storage architecture (SSA),integrated drive electronics (IDE), and/or any combination thereof.Storage 120 may include computer-readable media (e.g., hard disk drive,floppy disk drive, CD-ROM, and/or other type of rotating storage media,flash memory, EEPROM, and/or other type of solid state storage media)and may be generally operable to store data and/or programs (e.g., oneor more operating systems and/or one or more application programs).

I/O hub 115 may be communicatively coupled to firmware 130 via anysuitable interface such as SPI (System Packet Interface), LPC (Low PinCount) interface, for example. The information handling system 100 mayinclude one or more components that process and/or operate based onfirmware embedded in or coupled to the component. For example, suchcomponents may include hard disk drives (HDDs), CD-ROM drives, and DVDdrives, and/or various other devices and the like that includecontrollers driven by firmware. Firmware may be the program codeembedded in a storage device and maintained within or coupled to thedevice. The firmware for a component most often comprises theoperational code for the component.

More generally, firmware may include program code operable to control aplurality of information handling system 100 operations. System memory110, for example, may store firmware such as a basic input/output system(BIOS) program, and/or device drivers such as network interface card(NIC) drivers. A device driver may include program code operable tofacilitate interaction of a hardware device with other aspects ofinformation handling system 100. A BIOS program may include softwarethat facilitates interaction with and between the information handlingsystem 100 devices such as a keyboard, a mouse, and/or one or more I/Odevices. Information handling system 100 may operate by executing BIOSfor a system firmware in response to being powered up or reset. BIOS mayidentify and initialize components of system 100 and cause an operatingsystem to be booted.

I/O hub 115 may be communicatively coupled to nonvolatile memory 125 viaa PCIe interface, for example. Nonvolatile memory 125 may include, forexample, fast nonvolatile memory such as flash memory, NVDIMMs(nonvolatile dual in-line memory modules), a PCIe (Peripheral ComponentInterconnect Express) add-in-card, a direct connect nonvolatileinterface (e.g., an ONFI (Open NAND Flash Interface Working Group)interface), a SSD (solid-state drive), or another storage typeconfigured for fast restart. I/O hub 115 may be coupled to othercomponents (not shown) with optional interfaces (I/Fs) such as a PCIeinterface and device interfaces (I/Fs) such as a USB (Universal SerialBus) interface, for example.

Turning now to FIG. 2, a SAS drive plug connector (“SAS Connector”) inaccordance with the prior art is denoted generally with referencenumeral 200. As depicted in FIG. 2, the SAS drive plug 200 includes asignal segment 202 and a power segment 204. FIG. 2 a is a top view ofthe SAS connector 200 and FIG. 2 b is the bottom of the SAS connector200. The SAS connector 200 includes a signal segment 202 including pinsS1-S7 and S8-S14 as well as a power segment 204 with pins P1-P15. FIG. 3depicts the corresponding backplane receptacle connector for the SASConnector 200, denoted generally with reference numeral 300.

FIG. 4 depicts the pin count for a SAS connector in accordance with theprior art. As shown in FIG. 4, a typical SAS connector in accordancewith the prior art provides 2 differential lanes for data transfer.

FIG. 5 is an enhanced SAS Connector denoted generally with referencenumeral 500. FIG. 5 a is a top view of the enhanced SAS Connector 500and FIG. 5 b is a bottom view. As depicted in FIG. 5, the enhanced SASConnector 500 includes additional signal pins S15-S48, using the samewidth signals and ground pin pattern as pins S8-S14. FIG. 6 shows thecorresponding backplane receptacle connector for the enhanced SASConnector 500, denoted generally with reference numeral 600.

Specifically, FIG. 7 shows the pin count of the enhanced SAS connector500 in accordance with an embodiment of the present invention. As shownin FIG. 5-7, the enhanced SAS connector provides 5 and ½ additionaldifferential lanes, or 7 and ½ total lanes for data transmission. Aswould be appreciated by those of ordinary skill in the art, with thebenefit of this disclosure, slightly finer contacts may be used to allowthe connector 500 to support 6 additional data transmission lanes, or atotal of 8 lanes.

As would be apparent to those of ordinary skill in the art, although notshown in FIG. 5, the back end of the enhanced SAS connector 500 wouldalso be modified to provide two layers of pins contacting the PrintedCircuit Board (“PCB”). Contact patterns can be modified with less of thelonger ground contact, providing additional signal count when onlysingle ended signals are needed. As would be appreciated by those ofordinary skill in the art, with the benefit of this disclosure, otherpatterns may include dual ground isolation contacts for higher speedsignaling above 10 Gbps.

The system and methods disclosed herein may be used to supportmultiplexed or discrete signal operations at the controller end. A firstmode of operation for the enhanced SAS connector 500 of the presentinvention is depicted in FIG. 8. In this mode of operation, the signallanes are entirely separate between fabrics and the SAS and PCIe arediscrete signals at the connector. In this embodiment, 6 datatransmission lanes of the enhanced SAS connector 500 may be utilized. Inone embodiment, signal lane 1 502 and signal lane 2 504 which may beprovided by signals 51 through S14, would provide the two SAS signallanes. The signal lanes 3 505, 4 508, 5 510 and lane 6 512 may beprovided by signals S15 through S48 as shown in FIG. 7.

FIG. 8 a shows a SAS Input/Output Controller or SAS Redundant Array ofIndependent Disks (“RAID”) Controller 802 connected to a SAS HDD or SASSSD 804 through lane 1 502 and lane 2 504 of the enhanced SAS connector500. Similarly, FIG. 8 b shows a PCIe Card Slot or a PCIe Buffer Card808 connected to a PCIe SSD 806 through lanes 3-6 of the enhanced SASconnector 500. FIG. 8 c shows an exemplary embodiment with the PCIe SSD808 connected to a combined SAS and PCIe Storage Controller(“controller”) 810 through the enhanced SAS connector 5. As would beapparent to those of ordinary skill in the art, with the benefit of thisdisclosure, item 808 may alternatively be a SAS/SATA SSD or HHD.

In one embodiment, the controller 810 may be connected to a network,such as, for example, the Ethernet, through an Internet Small ComputerSystem Interface (“iSCSI”) 812 or another suitable interface. The iSCSI812 may be communicatively coupled to the processor or memory complex814 of the controller 810. The processor 814 may control the SAS IOcontroller 816 and the PCIe Switch 818. The SAS IO Controller 816 may beconnected to a SAS Expander 820 which can expand the SAS signals ontotwo separate lanes—i.e. lane 1 502 and lane 2 504. Similarly, the PCIeSwitch 818 may transmit signals through PCIe lane 1 (lane 3) 506, PCIeLane 2 (lane 4) 508, PCIe Lane 3 (lane 5) 510 and PCIe Lane 4 (lane 6)512. The signals from lane 1 502 and lane 2 504 may then be transmittedto a SAS device (not shown) while the signals from lane 3 506, lane 4508, lane 5 510 and lane 6 512 may be transmitted to the PCIe SSD 808.Accordingly, two paths for SAS provide compatibility with existing SASand SATA drives while four additional paths for PCIe or another fabricprovide forwards compatibility with a new fabric.

In another exemplary embodiment, the signal lanes of the enhanced SASconnector 500 may be multiplexed. In this embodiment, signal lanes maybe shared between the new fabric (Signals S15-S48) and the traditionalSAS lanes (S1-S14), for 4 to 8 lane fabric width. For instance, as shownin FIG. 9 c, four lanes may be utilized to transmit two SAS signals andfour PCIe signals. In this embodiment, the signals may be multiplexed atthe controller end, or there may be two different controllers that arephysically swapped out.

As shown in FIG. 9 a, lane 1 902 and lane 2 904 of the enhanced SASconnector 900 may be used to connect a SAS HDD or SAS SSD 910 to a SASIO Controller or SAS RAID Controller 912. Similarly, lane 1 902, lane 2904, lane 3 906 and lane 4 908 may connect the PCIe SSD 914 to a PCIeCard Slot or Buffer Card 916. As shown in FIG. 9 c, in anotherembodiment, the PCIe SSD 914 may be connected to a combined SAS and PCIeStorage Controller (“controller”) 916. As would be apparent to those ofordinary skill in the art, with the benefit of this disclosure, item 914may alternatively be a SAS/SATA SSD or HHD.

In one embodiment, the controller 916 may be connected to a network,such as, for example, the Ethernet, through an iSCSI 918 or anothersuitable interface. The iSCSI 918 may be communicatively coupled to theprocessor or memory complex 920 of the controller 916. The processor 920may be communicatively coupled to a PCIe Switch 922 and a SAS JOController 924. The SAS IO Controller 924 may in turn be communicativelycoupled to a SAS Expander 926. Each of the PCIe Switch 922 and the SASExpander 926 may be connected to a multiplexer 928. The multiplexer 928selects which of the SAS signal from the SAS expander 926 and the PCIesignal from the PCIe switch 922 will be directed to each lane of theenhanced SAS connector 900. Accordingly, in the exemplary embodiment,lane 1 902 and lane 2 904 may be operable to transmit both SAS and PCIedata while lane 3 906 and lane 4 908 transmit only PCIe data.

A discovery process is required at the PCIe controller or device toinsure a SAS device or controller plugged into the system does not getdriven by PCIe signals. Once the discovery process is completed, thecontroller may use all lanes, including the traditional SAS lanes, S1through S14.

As would be appreciated by those of ordinary skill in the art, with thebenefit of this disclosure, variations on the end storage devices andsource controller devices are possible, including division of the enddevice ports into dual ×4 lanes for high availability.

Accordingly, signal lanes are added to the backside of the SAS/SATAdevice connectors, in support of protocols with greater widths than ×2supported by SAS. In one embodiment, a PCIe device in a 2.5 inch formfactor may be placed in the same or a similar slot to a 2.5 inch SATA orSAS drive.

Although the present disclosure has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereto without departing from the spirit and the scope of theinvention as defined by the appended claims. Various changes,substitutions, and alterations can be made to interfaces with multipledevices at one end and a single device at the other end withoutdeparting from the spirit and the scope of the invention.

1. An enhanced serial attached small computer system interface for aninformation handling system comprising: a receptacle; wherein thereceptacle is connectable to an information handling system; and aconnector; wherein the connector is connectable to the receptacle; andwherein the connector comprises: a first set of signal pins positionedon a first planar surface of the connector; a second set of signal pinspositioned on a second planar surface of the connector; wherein thesecond planar surface is not co-planar with the first planar surface;and a third set of signal pins positioned on a third planar surface ofthe connector; wherein the third planar surface is not co-planar withthe first planar surface and the second planar surface.
 2. The enhancedserial attached small computer system interface of claim 1, furthercomprising a set of power pins, wherein the set of power pins arepositioned on the first planar surface of the connector.
 3. The enhancedserial attached small computer system interface of claim 2, wherein theset of power pins comprises fifteen pins.
 4. The enhanced serialattached small computer system interface of claim 1, wherein the firstset of signal pins comprises seven pins.
 5. The enhanced serial attachedsmall computer system interface of claim 1, wherein the second set ofsignal pins comprises thirty seven pins.
 6. The enhanced serial attachedsmall computer system interface of claim 1, wherein the third set ofsignal pins comprises four pins.
 7. The enhanced serial attached smallcomputer system interface of claim 1, wherein the first set of signalpins, the second set of signal pins and the set of power pins arelocated on a first side of the enhanced serial attached small computersystem interface; and wherein the third set of signal pins is located ona second side of the enhanced serial attached small computer systeminterface.
 8. The enhanced serial attached small computer systeminterface of claim 1, wherein the first set of signal pins, the secondset of signal pins and the third set of signal pins provide at leastseven differential lanes for data transfer.
 9. A method of selectivelytransferring data over a PCIe path or a SAS path comprising: connectingan enhanced connector with a first set of connection lanes and a secondset of connection lanes to one or more controllers; wherein thecontroller controls the connection lanes; wherein the first set ofconnection lanes are operable as a PCIe signal path; wherein the secondset of connection lanes are operable as a SAS signal path; connectingthe first set of connection lanes to a PCIe data storage device; andconnecting the second set of connection lanes to a SAS data storagedevice.
 10. The method of claim 9, wherein the one or more controllerscomprises: a PCIe controller; wherein the PCIe controller controls thefirst set of connection lanes; and a SAS controller; wherein the SAScontroller controls the second set of connection lanes.
 11. The methodof claim 9, wherein the one or more controllers comprises a combined SASand PCIe storage controller.
 12. The method of claim 11, wherein thecombined SAS and PCIe storage controller comprises: a processor; a PCIeswitch communicatively coupled to the processor; wherein the PCIe switchcontrols the operation of the first set of connection lanes; a SASinput/output controller communicatively coupled to the processor; and aSAS expander communicatively coupled to the SAS input/output controller;wherein the SAS expander controls the operation of the second set ofconnection lanes.
 13. A method of selectively transferring data over aPCIe path or a SAS path comprising: connecting an enhanced connectorwith a first set of connection lanes and a second set of connectionlanes connected to one or more controllers; wherein the one or morecontrollers control the connection lanes; wherein the first set ofconnection lanes are operable as a PCIe signal path; wherein the secondset of connection lanes are optionally operable as a SAS signal path ora PCIe signal path; connecting the first set of connection lanes to aPCIe data storage device; and connecting the second set of connectionlanes to a data storage device selected from the group consisting of aSAS data storage device and a PCIe data storage device.
 14. The methodof claim 13, wherein the first set of connection lanes is connected to aPCIe controller.
 15. The method of claim 13, wherein the second set ofconnection lanes is connected to one of a PCIe controller and a SAScontroller.
 16. The method of claim 13, wherein the enhanced connectoris connected to a combined SAS and PCIe controller.
 17. The method ofclaim 16, wherein the combined SAS and PCIe controller comprises: aprocessor; a PCIe switch communicatively coupled to the processor;wherein the PCIe switch is operable to control the first set ofconnection lanes and the second set of connection lanes; a SASinput/output controller communicatively coupled to the processor; a SASexpander communicatively coupled to the SAS input/output controller;wherein the SAS expander is operable to control the second set ofconnection lanes; and a multiplexer connected to the PCIe switch and theSAS expander; wherein the multiplexer determined which of the SASexpander and the PCIe switch controls the second set of connectionlanes.